Slipper-type pumping element for a pump or motor

ABSTRACT

A slipper vane sealed pump is proportioned in critical relationships between the pumping vane and the cam bore: 1. WIDTH TO CONTACT DEPTH ASPECT RATIO OF 2.6 TO 2.8; 2. CIRCUMFERENTIAL CONTACT ARC TO CONTACT DEPTH RATIO OF 1.4 TO 1.9; 3. UNDERSLIPPER SURFACE CURVATURE WITHIN A RANGE OF 2 1/2 TO 5 PERCENT OF SPRING RADIUS; AND 4. A SPRING RATIO OF 1.55/1; TO AFFORD IMPROVED NOISE AND HIGH SPEED DURABILITY CHARACTERISTICS.

United States Patent Carlson Mar; 19, 1974 SLIPPER-TYPE PUMPING ELEMENT FOR A PUMP OR MOTOR Primary Examiner-C. J. Husar Attorney, Agent, or Firm-Hill, Sherman, Meroni, Gross & Simpson 5 7] ABSTRACT A slipper vane sealed pump is proportioned in critical relationships between the pumping vane and the cam bore:

1. width to contact depth aspect ratio of 2.6 to 2.8; 2. circumferential contact are to contact depth ratio of 1.4 to 1.9; 1 3. underslipper surface curvature within a range of 2% to 5 percent of spring radius; and 4. a spring ratio of 1.55/1; to afford improved noise and high speed durability characteristics.

7 Claims, 5 Drawing Figures (PRIOR ART) BACKGROUND OF THE INVENTION 1. Field of the Invention The invention described herewith refers exclusively to a species of pump, sometimes operable as a motor, known as a slipper vane pump. More specifically, the present invention relates to a specific construction of slipper pumping vane for a pump of the expanding chamber type wherein the tangent are or crossover point is sealed by interposing a minimum of one slipper pumping vane in the tangent arc sealing position at all times.

2. The Prior Art 7 While slipper pump art is copiously represented by the prior art patents of William H. Livermore, Hubert M. Clark and Gilbert H. Drutchas, most of such art is centered on a form known to persons skilled in the art as a tangent arc seal. Such pump-type characteristically provides a rotor diameter seal at the crossover point between the outlet and inlet ports of a typical expanding chamber-type pumping unit.

The general concept of a so-called slipper seal design wherein a minimum of one slipper is interposed into a tangent arc sealing position at all times has been described in the prior art. However, none of the pump constructions heretofore disclosed in.the prior art are capable of meeting the noise and high speed durability characteristics vital to achieving the current order of sophistication required for high pressure hydraulic power applications, for example, for use as power steering pumps on dirigible vehicles. Due to the complexity of the noise-generating phenomena and the dynamic perturbations resulting from the virtual free body action of the slipper pumping vane, concise positioning and specific geometric proportions are absolutely essential in order to achieve a pump which is satisfactory for widespread commercial usage and in order to achieve a status of commercial acceptability.

The increased stroke required on some applications to accommodate larger power requirements has been difficult to attain with a pump utilizing conventional slipper configurations. The higher bore accelerating characteristics have led to premature failures in some cases due to so-called slipper vane over-rock. Such problem is even further compounded in attempting to achieve a slipper seal rather than a tangent arc seal. Usually the number of slippers is increased, thereby of necessity narrowing the cam bore size and presenting problems of increased difficulty with respect to the control of the ensuing critical dynamic action.

A typical prior art slipper is depicted in FIG. 1 of the drawings wherein is shown a slipper pumping vane which has been in widespread commercial usage since at least 1965. In such structure wherein a tangent seal is utilized, there is provided a slipper pumping veane which has a substantial width to drive ratio (W/D). Further, the lesser number of slipper pump vanes permits vanes to be utilized which have a large mass (M) and thus the centrifugal force (C.F.) acting on the pumping vanes is higher than for slippers having a smaller mass. The slipper pumping vanes are also characterized by a so-called lift ramp provided for buoying the slipper pumping vane in a generally radially outward direction.

For optimum stability, the slipper pump vane is perched on the edge of the rotor slot.

SUMMARY OF THE INVENTION In accordance with the present invention, a slipper seal rotor and slipper relationship has been determined which affords concise positioning and specific geometricproportions essential to a successful pump. Thus, the pump of the present invention has a slipper construction which afiords a lower width to drive ratio (W/D). Moreover, since a larger number of slippers are utilized, the comparative mass of each respective slipper is reduced, thereby resulting in less centrifugal force (C.F.) being exerted on an individual slipper pumping vane element.

A lift ramp is not required but a so-called plane-in notched in the rotor at the edge of the slot can be utilized.

By my invention, it is recognized that a narrow selective drive band optimizes stability with a minimum drive moment.

The present invention also provides an underslipper surface curvature affording contact with a spring to avoid excessive column action, thereby reducing spring wear and avoiding increased slipper height.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross-sectional view of a prior art arrangement showing a typical slipper pumping vane of the type used in a pump having tangent arc sealing.

FIG. 2 is a view similar to FIG. 1 but showing the novel slipper pumping vane of the present invention as embodied in a slipper seal pump as contemplated by the present invention.

FIG. 3 is a view similar to FIG. 2 but showing additional details and relationships between the various parts of the pump in accordance with the principles of the present invention.

FIG. 4 is an end elevational view of the slipper seal pumping element provided in accordance with the principles of the present invention; and

FIG. 5 is a side elevational view of the slipper pumping vane element of FIG. 4.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 depicts a prior art arrangement which has been in widespread commercial usage since 1965. Thus, there is a cam ring 10 having a cam bore 11 forming the outer wall of a pumping chamber formed with an inlet side and an outlet side, the respective sides being designated by legend.

Rotatable within the pumping chamber is a rotor 12 having a plurality of peripheral slots 13 each formed with a bottom wall 14 against which is bottomed one end of a coil spring 16. The other end of the coil spring 16 is engaged against a curved surface or undersurface 17 of a slipper-type pumping element 18 having two outboard areas 19 and 20 on opposite sides of a center recess 21. One of the side flanks of the slipper-type pumping element 18 is formed with a lift ramp 22.

The width of the slipper-type pumping element 18 is indicated at W and the depth of the working arc in the pumping chamber is indicated at D. The legend C.F. is indicated to show the effects of centrifugal force and the center of gravity of the pumping vane is shown at C.G. It will be understood that the pump of FIG. 1 uses a tangent arc seal, i.e., the diameter of the rotor 12 seals against the bore wall 11 at a crossover point between the outlet and inlet ports. In this regard, it will be understood that the bore wall 11 can either be a single-lobed arrangement with a single inlet port and single outlet port or a double-lobed or multiple-lobed pumping chamber can also be provided so that there is more than a single pumping impulse on a single rotation of the rotor 12..By virtue of the prior art arrangement shown in FIG. 1, a lesser number of slippers permits a large mass indicated at M. The slipper of FIG. 1

exhibits a substantial width-to-drive ratio (W/D) and the lift ramp 22 tends to buoy the slipper outwardly during operation.

Current requirements for a slipper seal characteristic together with requirements for increased stroke and higher displacements leads to additional complexities in the bore-to-slipper relationship.

Generally, in order to make a slipper seal design, a larger number of slippers are required to insure that at least one slipper will be interposed in the tangent arc sealing position at all times. The increased number of slippers, however, in turn, leads to the need for lessening the width of the slipper to fit the limited radial and circumferential area available on the rotor to permit sufficient rotor spacing land between the adjacent slippers. The lessening of the width of the slipper, in turn, results in a dynamic over-rock condition since the narrower slipper with its lower mass has less centrifugal force and less guide on the bore periphery, there being a large clearance on the edge of the rotor slot.

In accordance with the present invention, however, a compensating factor of less clearance is provided, thereby insuring a constraint against overrocking and improving stability. This is effected by careful control of the position of engagement between the rotor and the flank of the slipper pumping vane. Thus, in order to afford the necessary stability to operate at high speeds, there must be minimum drive moment.

In FIG. 2, the slipper pumping vane of the present invention is shown generally at 30. In FIG. 3 the forces acting on the slipper are depicted assuming direction of rotation in a counterclockwise direction, as shown by the arrow 31 applied at the edge of the slot or notch.

The driven slipper reacts virtually through a point designated in FIG. 3 at point which constitutes a pivot or rotation point at the front of the slipper pumping vane. Thus, the stable case-moments acting on the slipper are:

( Drli-e) Frlc 1/2 It may be noted that friction and centrifugal force are the only factors preventing the slipper pumping vane from rotating about the point 0.

The unstable case-moments are:

(FDFUQ)(D) Frlc 3 1k 5) It may be noted the tendency to be unstable increases at W O, D a, or the moment Mpfl a.

Noise control due to the need of sealing in the tangent arc with the slipper is most critical. Therefore, the slipper-to-slot clearances must be held at tight as possible within manufacturing limits. A slipper configured to ride high in the slot increases slipper clearance in the working arc. In accordance with the principles of this invention, it has been determined that the following proportion is critical: slipper width (W) measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D 2.6 to 2.8.

Turning now to FIG. 4, the slipper per se is shown and it will be noted that the slipper has a curved flank surface 32 on one side and a curved flank surface 33 on the other side. Further, there is an underslipper surface 34 and an upper slipper surface divided into two sections 36 and 37 separated by a center relieved recess 38. Thus, the upper surface sections 36 and 37 determine the circumferential contact are which is designated C The contact depth measured on the slipper is from the tangent to the top surface 36 and/or 37 and the center of the driving flank 32 and such depth is indicated at D.

In accordance with the principles of the present invention, the following proportion is critical: circumferential contact arc to contact depth ratio C /D E 1.4 to 1.9.

Still another critical characteristic is the form of the slipper bottom contour vis-a-vis the life and operation of the support spring. Whereas the wider slipper used in the tangent seal design such as the slipper 18 (FIG. 1) was substantially round, it has been discovered that a particular curve form, as provided by the present invention, is optimal to insure sufficient spring life. Thus, the slipper surface or underslipper surface must contact at, or near, the center of the spring in order to avoid excessive column action. An arc is necessary so that surface, rather than point contact, is obtained. That relationship reduces spring wear. Moreover, the

slipper geometry requires a flat curve to avoid increasing slipper height.

As shown in FIG. 2, the height of the spring is indicated at S,,, while the diameter of the spring is indicated at S It is contemplated by this invention that the underslipper surface curvature be formed as shown at 34 to allow unencumbered spring rock without attrition to the spring in its shrouding guide hole. Analytically, such relationship is defined as a curve whose curvature departs within a range of 2% to 5 percent of the spring radius measured from the spring center.

Further, it has been determined that a spring ratio, i.e., the ratio of the length of the spring S, to the diameter of the spring 5,, of 1.55/1 or less in the installed position provides the proper relationship for good spring geometry, pump geometry and the dynamic aspects, i.e., the rate of bore acceleration, etc. for a successful pump operation.

It will be understood that the pump of the present invention, as shown in FIGS. 25, inclusive, has a housing having a cam bore wall forming a pumping chamber for a pump of the expanding chamber type and specifically including a crossover are disposed between respective inlet and outlet portions of the pumping chamber and a rotor in said pumping chamber having a plurality of circumferentially spaced apart peripheral notches for carrying a corresponding plurality of slipper vanes and such notches and vanes being sufficient in number to position at least one such vane in the crossover arc at all times.

By providing a slipper with a width and a contact are and an underslipper surface curvature determined in accordance with the limitations herein defined, the essential relationship pertaining to the slipper cam bore will be established so that an effective slipper seal can be achieved in a pump capable of meeting the noise and high speed durability characteristics in a commercially feasible pump.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. A pump comprising a housing having a cam bore wall forming a pumping chamber for a pump of the expanding chamber type and specifically includinga crossover are disposed between respective inlet and outlet portions of the pumping chamber,

a rotor in said pumping chamber having a plurality of circumferentially spaced apart peripheral notches for carrying a corresponding plurality of slipper vanes and such notches and vanes being sufficient in number to position at least one such vane in the crossover are at all times,

and each such slipper vane being constructed to exhibit the following proportions relating to the slipper cam bore relationship; I

l. a slipper width in specified dimension, i.e., a slipper width measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D E 2.6 to 2.8,

2. a circumferential contact are on the outer surface of said slipper of specified dimension, i.e., a circumferential contact are to contact depth ratio C /D 1.4 to 1.9, and

3. an underslipper surface curvature formed on said slipper to allow unencumbered spring rock without attrition to the spring in its shrouding guide hole, i.e., a curvature on any curve whose curvature departs within a range of 2% to 5 percent of the spring radius measured from the slipper center and wherein the spring ratio (S /S is 1.55/1 or less in the installed position.

2. For use in a pump of the type having a notched rotor rotatable in a pumping chamber forming a working arc, the improvement of a spring-biased slipper type pumping vane particularly characterized by:

l. a slipper vane width (W) to contact depth aspect ratio in the order of about from 2.6 to 2.8, wherein W is measured at the maximum protuberance of the slipper vane flank and wherein the contact depth aspect ratio is W/D, D being the depth of the working arc;

2. a circumferential contact arc (C to contact depth ratio in the order of about from 1.4 to 1.9 (CA/D);

3. the underslipper surface curvature is a curve whose curvature departs within a range of in the order of about 2% to 5 percent of the spring radius measured from the slipper center;

and wherein 4. the spring has a spring ratio of no more than 1.55/1 in the installed position, wherein the spring ratio is the proportion of the length of the spring to the diameter thereof (S /S 3. For use in a slipper pump, a slipper having a slipper width W, a contact depth D and a circumferential contact are C and wherein the slipper width measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D 2.6 to 2.8 and wherein the circumferential contact are to contact depth ratio C /D equals 1.4 to 1.9.

4..For use in a slipper pump, a slipper having an underslipper surface curvature formed to allow unencumbered spring rock without attrition to the spring and its shrouding guide hole,

said curvature constituting a curve whose curvature departs within a range of 2% to 5 percent of the spring radius measured from the slipper center.

5. In a slipper pump having a sufficient number of slippers so that at least one slipper will be interposed in a tangent arc sealing position at all times, the improvement of a slipper exhibiting the following proportions relating to theslipper cam bore relationship:

1. a slipper width measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D 2.6 to 2.8; and

2. a circumferential contact arc to contact depth ratio C /D 1.4 to 1.9.

6. In a slipper pump as defined in claim 5 said slipper being further characterized by an underslipper surface curvature constituting a curve whose curvature departs within a range of 2% to 5 percent of the spring radius measured from the slipper center.

7. In a slipper pump as defined in claim 6, a spring biasing the slipper radially outwardly and having a spring ratio of 1.55/1 or less in the installed position wherein the spring ratio constitutes the proportion of the length of the spring to the diameter thereof. 

1. A pump comprising a housing having a cam bore wall forming a pumping chamber for a pump of the expanding chamber type and specifically including a crossover arc disposed between respective inlet and outlet portions of the pumping chamber, a rotor in said pumping chamber having a plurality of circumferentially spaced apart peripheral notches for carrying a corresponding plurality of slipper vanes and such notches and vanes being sufficient in number to position at least one such vane in the crossover arc at all times, and each such slipper vane being constructed to exhibit the following proportions relating to the slipper cam bore relationship;
 1. a slipper width in specified dimension, i.e., a slipper width measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D congruent 2.6 to 2.8,
 2. a circumferential contact arc on the outer surface of said slipper of specified dimension, i.e., a circumferential contact arc to contact depth ratio CA/D 1.4 to 1.9, and
 3. an underslipper surface curvature formed on said slipper to allow unencumbered spring rock without attrition to the spring in its shrouding guide hole, i.e., a curvature on any curve whose curvature departs within a range of 2 1/2 to 5 percent of the spring Radius measured from the slipper center and wherein the spring ratio (SL/SD) is 1.55/1 or less in the installed position.
 2. a circumferential contact arc on the outer surface of said slipper of specified dimension, i.e., a circumferential contact arc to contact depth ratio CA/D 1.4 to 1.9, and
 2. For use in a pump of the type having a notched rotor rotatable in a pumping chamber forming a working arc, the improvement of a spring-biased slipper type pumping vane particularly characterized by:
 2. a circumferential contact arc (CA) to contact depth ratio in the order of about from 1.4 to 1.9 (CA/D);
 2. a circumferential contact arc to contact depth ratio CA/D 1.4 to 1.9.
 3. For use in a slipper pump, a slipper having a slipper width W, a contact depth D and a circumferential contact arc CA and wherein the slipper width measured from the maximum protuberance of each slipper flank to contact depth aspect ratio of W/D 2.6 to 2.8 and wherein the circumferential contact arc to contact depth ratio CA/D equals 1.4 to 1.9.
 3. an underslipper surface curvature formed on said slipper to allow unencumbered spring rock without attrition to the spring in its shrouding guide hole, i.e., a curvature on any curve whose curvature departs within a range of 2 1/2 to 5 percent of the spring Radius measured from the slipper center and wherein the spring ratio (SL/SD) is 1.55/1 or less in the installed position.
 3. the underslipper surface curvature is a curve whose curvature departs within a range of in the order of about 2 1/2 to 5 percent of the spring radius measured from the slipper center; and wherein
 4. the spring has a spring ratio of no more than 1.55/1 in the installed position, wherein the spring ratio is the proportion of the length of the spring to the diameter thereof (SL/SD).
 4. For use in a slipper pump, a slipper having an underslipper surface curvature formed to allow unencumbered spring rock without attrition to the spring and its shrouding guide hole, said curvature constituting a curve whose curvature departs within a range of 2 1/2 to 5 percent of the spring radius measured from the slipper center.
 5. In a slipper pump having a sufficient number of slippers so that at least one slipper will be interposed in a tangent arc sealing position at all times, the improvement of a slipper exhibiting the following proportions relating to the slipper cam bore relationship:
 6. In a slipper pump as defined in claim 5 said slipper being further characterized by an underslipper surface curvature constituting a curve whose curvature departs within a range of 2 1/2 to 5 percent of the spring radius measured from the slipper center.
 7. In a slipper pump as defined in claim 6, a spring biasing the slipper radially outwardly and having a spring ratio of 1.55/1 or less in the installed position wherein the spring ratio constitutes the proportion of the length of the spring to the diameter thereof. 